1. Field of the Invention
The present invention relates to a resonance generator, more specifically, to a resonance generator which imitates an acoustic piano string resonance generated when a damper pedal is operated.
2. Description of the Related Art
In an acoustic piano, a playing method is used in which operation that a damper pressing a string is released from the string by a damper pedal is performed, and not only a string that was actually pressed but also all other strings are vibrated in response to resonance. In electronic musical instruments such as electronic pianos and electronic organs, a function to imitate string resonance generated in response to this damper pedal operation is required.
For example, a normal sound of a piano without pedaling down its damper pedal and a sound of the piano including resonance when the damper pedal is pedaled down are recorded and their waveform data are stored, and depending on operation of the damper pedal, a waveform is selected to produce a music sound.
There is available another method in which, after the sound of the piano including resonance when the damper pedal is pedaled down is recorded, only harmonic overtone components are removed from this piano sound to generate resonance components, and waveform data of the resonance components are stored, and when the damper pedal is pedaled down, the resonance components are generated together with a normal music sound.
In Japanese Unexamined Patent Publication No. H09-127941, an electronic instrument is proposed in which the electronic instrument includes a resonance memory for storing waveform data of a music sound obtained by removing a reference tone from a music sound including resonance of the reference tone and controls amplitude of the waveform data readout from the resonance memory in response to an instruction generated by the damper pedal operation.
There is also available a method in which, instead of producing a music sound based on waveform data stored in advance, a resonance circuit is constructed by using a digital signal processor (DSP) so as to output a signal forming resonance through the resonance circuit only when the damper pedal is operated.
[Patent Document 1] JP 09-127941 A
In playing accompanying an operation of a damper pedal, key pressing after pedaling down the damper pedal and pedaling down the damper pedal after key pressing are possible. In the conventional technique in which a resonance circuit is constructed by using the DSP, a satisfactory resonance cannot be obtained when the damper pedal is pedaled down after key pressing.
On the other hand, in the electronic instrument using waveform data stored in advance as disclosed in Patent document 1, an amplitude of the waveform data is controlled according to a timing instructed by the damper pedal, so that when the damper pedal is pedaled down after key pressing, it is possible to make smaller the amplitude of the waveform data of the resonance according to an elapsed time until the key pressing from the damper operation and output it.
However, when a key is pressed after the damper pedal is pedaled down, resonance with high intensity caused by the pressing impact sound on the key is generated, and on the other hand, when the damper pedal is pedaled down after key pressing, resonance with low intensity caused by small vibration that does not include a key pressing impact sound is generated. These two kinds of resonances are different in envelope from each other, so that only by reading out data on a single resonance in the operation timing of the damper pedal, resonance with high accuracy cannot be reproduced.